The background of the invention will be discussed in two parts:
1. Field of the Invention
This invention relates to machines for applying roofing material, and more particularly to a machine for joining together adjacent overlying edges of roll roofing material where the facing edges are composed in part of a bitumen material.
2. Description of the Prior Art
Roofing material has generally been composed of a tar or pitch-like material, with such roofing material being commercially available in rolls. Such materials are usually applied to a roofing substrate such as plywood or the like by rolling out one strip or sheet of material with a second strip being rolled out thereafter with the edges overlapping. Normally, prior to the rolling out of the roofing material, a liquid or molten tar-like material is applied to the substrate or roof, the roofing material is suitably positioned on this liquid or molten tar to provide adhesion to the roof with subsequent strips or sheets of material having the overlapping edges suitably sealed by a liquid or molten tar interposed between facing edges. The upper edge surface is then pressed toward the lower edge to seal the joint.
New roofing materials have been developed which are particularly suitable for gently sloping or flat roofs more commonly found in industrial or commercial buildings. One such roofing material is manufactured by Koppers Company, Inc. of Pittsburgh, Pennsylvania under the trademark "KMM", and is referred to as the KMM membrane roofing material. Two such roofing materials are available, both of these materials being five-layer laminates. The standard material is provided with a polyethylene outer surface with a layer of bitumen, a plastic core, a second layer of bitumen, and an opposing outer layer of polyethylene. The second material available under the "KMM" mark is likewise a laminate composed of a thick, flexible plastic core which is protected on each side with a layer of modified bitumen with the top surface being a heavy embossed aluminum foil, and the bottom surface being a film of polyethylene. This material supplied in roll form with a four inch edge on the upper surface being polyethylene. That is, the upper surface of aluminum foil terminates four inches before the edge with this four inches having the polyethylene membrane, this edge being adapted for adhesion to a four inch portion of the under surface of an adjacent edge upon application of heat and pressure.
Conventional methods for applying this roofing material involved the use of three, four or five men. The first step in the operation is to roll out the first strip of material. A second strip of material is then rolled out in overlying overlapping relationship consistent with the four inch polyethylene upper surface thereby preliminarily forming an edge of four inches in width with facing polyethylene surfaces. A worker then comes along and bends back four inches (or more) of the upper sheet or strip to expose the upper and lower polyethylene surface. Another worker trails behind the first worker with a propane torch to heat the upper and lower edge portions. This method is referred to as a "heat fusion" method. The application of the heat by direct flame breaks and draws apart the external plastic or polyehylene film and melts the bitumen until it is plastic enough to flow under pressure. The second worker is normally working on his hands and knees and after observing proper breakdown of the polyethylene film and proper melting of the bitumen, he then manually pushes the upper sheet into overlapping relation with the lower sheet to provide a measure of adhesion. A third worker trails behind the second worker with a propane torch to reheat the surface along the edge with a fourth worker trailing behind with a heavy weighted roller which is rolled back and forth to apply pressure to the edge.
With such a manual process, many problems result. If the second worker is applying too little heat, the polyethylene film is not breaking down properly and the bitumen is not at the proper plastic state for optimum adhesion. If he is applying too much heat, the bitumen becomes liquid rather than plastic resulting in improper adhesion as well as an unsightly flow of the bitumen out of the overlapping edge area. Likewise, if the third worker is reheating the aluminum surface at the edge improperly, the same less than optimum result is achieved. Furthermore, with the bitumen in a liquid state, the roller gathers the molten bitumen thereby requiring cleaning frequently with needless down time. Other problems can arise if the workers are not operating as a team or if the work is interrupted for any reason. Generally, an unskilled work crew using this manual method will result in unsightly edges where the bitumen material has flowed irregularly out from the overlapping region and even worse, improper adhesion resulting from lack of uniformity or consistency in the heating and rolling process results in voids and uneven distribution of the bitumen within the overlapping region. In such cases, the edges can be readily separated where improper heat and pressure has been applied. The rolling operation often times results in a gathering or puckering of the upper layer of material thus further adding to the unsightliness as well as the imperfection of the bond.
Furthermore, since roofing material is applied on the exterior of the building ambient conditions produce variables of temperature and humidity which affect the amount of heat to be applied, the timing of the application of heat and pressure as well as other factors.
It is an object of this invention to provide a new and improved machine for joining adjacent strips of roofing material together in overlapping relation.
It is another object of this invention to provide a new and improved machine for applying adjacent sheets of a roofing material together in an overlapping relation to provide a uniform bond between the adjacent surfaces of the overlapping edges.